Drip irrigation emitters are generally known for use in delivering irrigation water to a precise point at a predetermined and relatively low volume flow rate to conserve water. Drip irrigation emitters may be used in water conduits such as drip tape or extruded pipe, to supply water at a slow, controlled rate to the root zone of the plants being irrigated. The emitters may be inserted into and bonded with the water conduit wall at regular intervals. Each emitter may conduct water from the interior to the exterior of the conduit at a reduced pressure and at a lower rate.
As the water travels through the conduit away from the water source, the water pressure decreases. Water pressure at the beginning of the conduit may be greater than at the far end of the conduit. Other field conditions, such as elevation, also affect the water pressure, and thus the drip rate, along the length of the water conduit. Changes in drip rate are a problem because some areas may receive too much or too little water, and it is desirable to have a relatively uniform drip rate along the length of the water conduit. To reduce the effect of the pressure differences over the length of the conduit, some drip irrigation emitters have been developed that are pressure compensating or flow rate regulated. Pressure compensating or flow rate regulated emitters allow increasing the length of the water conduit while having substantially uniform drip rates along the conduit's length, and may cover larger areas more economically.
U.S. Pat. Nos. 6,039,270 and 7,681,805 show examples of integral flow regulated emitters that are generally disc shaped. These emitters have a relatively large thickness including three levels stacked together, and a relatively small filter area. Water from the water conduit flows through all three levels of the emitter. The first level includes a relatively small filter area facing the inside space of the conduit, along with a water entrance chamber and part of the pressure reducing path or labyrinth. The second level, which is separated from the first level by a diaphragm or elastomeric membrane, includes a continuation of the pressure reducing path or labyrinth, and a regulation chamber. The third level, which is bonded to the conduit wall, includes an exit pool adjacent an opening in the conduit wall.
It is desirable to reduce or minimize the size and thickness of integral disc shaped drip irrigation emitters. For example, reducing the size and thickness of the emitters is advantageous because it can result in savings in the cost of materials. For single use applications, in which a drip tape may be removed from the field for disposal or recycling after each growing season, it would be advantageous and desirable to have emitters that are lower in cost.
Additionally, reducing the size and thickness of the emitters also would help in packaging and shipping. After the water conduit has integrated emitters in place, it is a common procedure to roll the drip line for packaging and shipping. However, each emitter has a thickness that may cause a bulge or lump that increases the difficulty of rolling and packaging the conduit, especially with thin walled drip tape, e.g., 15 mil or less. A drip irrigation emitter is needed having reduced size and thickness to facilitate packaging and shipping of thin walled drip tape or conduit.
There also is a need for a disc shaped drip irrigation emitter that reduces or minimizes the cost and size of the diaphragm, or elastomeric membrane, used for pressure regulation. The diaphragm is an elastomeric element that must flex in accordance with the water pressure differential on both sides of the diaphragm. The elastomer material may be rather costly, and attempts to replace the elastomeric element with other less costly materials have not been successful because other materials are not sufficiently flexible over time due to compression set of the material, and as a result may decrease the flow rate to an unacceptable rate.
Additionally, there is a need for a drip irrigation emitter that has a relatively large filtering area to provide a sufficient volume of water into the emitter. In drip irrigation systems, it is important to filter debris or other matter to prevent it from blocking or restricting flow through the emitter pressure reducing flow passage and outlet. However, it is increasingly difficult to provide a large filtering area if the emitter is reduced in size. A disc shaped pressure regulated emitter is needed having a large filtering area and a very small thickness.